Well after reading Datonking's "Lag Teleport" thread it gave me an idea of what I used to do back in the day when I was grinding to 60. This only works of you have the understanding and control of turning your router on and off (button or command hotkey).
Ok well if you know how to do this then it is very simple. When another enemy/ies engage you that you know you can not take;
1) Hit your hotkey or button to disconnect your router.
2) Run over to a spot behind a tree or place where they won't see you.
3) Reconnect your router.
4) Mount up an RUN!
A few points to consider... You have 15 seconds to get to where you want to be and reconnect your router before you are disconnected from the server. When you are disconnected, the time you spent running to another spot won't have registered because you will have never connected again and you will most certainly be dead by the time you log back in.
Also, after you have reconnected you will receive tremendous lag (enough to put you from green to red) and things will be slow for about 20-30 seconds afterward.
~Edit~
To them you will appear to be there one second and once you have reconnected... POOF... you will disappear!